ALTER SEQUENCE
Section: PostgreSQL 15.6 Documentation (7)
Updated: 2024
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NAME
ALTER_SEQUENCE - change the definition of a sequence generator
SYNOPSIS
ALTER SEQUENCE [ IF EXISTS ] name
[ AS data_type ]
[ INCREMENT [ BY ] increment ]
[ MINVALUE minvalue | NO MINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE ]
[ START [ WITH ] start ]
[ RESTART [ [ WITH ] restart ] ]
[ CACHE cache ] [ [ NO ] CYCLE ]
[ OWNED BY { table_name.column_name | NONE } ]
ALTER SEQUENCE [ IF EXISTS ] name SET { LOGGED | UNLOGGED }
ALTER SEQUENCE [ IF EXISTS ] name OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER SEQUENCE [ IF EXISTS ] name RENAME TO new_name
ALTER SEQUENCE [ IF EXISTS ] name SET SCHEMA new_schema
DESCRIPTION
ALTER SEQUENCE
changes the parameters of an existing sequence generator. Any parameters not specifically set in the
ALTER SEQUENCE
command retain their prior settings.
You must own the sequence to use
ALTER SEQUENCE. To change a sequence's schema, you must also have
CREATE
privilege on the new schema. To alter the owner, you must also be a direct or indirect member of the new owning role, and that role must have
CREATE
privilege on the sequence's schema. (These restrictions enforce that altering the owner doesn't do anything you couldn't do by dropping and recreating the sequence. However, a superuser can alter ownership of any sequence anyway.)
PARAMETERS
name
-
The name (optionally schema-qualified) of a sequence to be altered.
IF EXISTS
-
Do not throw an error if the sequence does not exist. A notice is issued in this case.
data_type
-
The optional clause
AS data_type
changes the data type of the sequence. Valid types are
smallint,
integer, and
bigint.
Changing the data type automatically changes the minimum and maximum values of the sequence if and only if the previous minimum and maximum values were the minimum or maximum value of the old data type (in other words, if the sequence had been created using
NO MINVALUE
or
NO MAXVALUE, implicitly or explicitly). Otherwise, the minimum and maximum values are preserved, unless new values are given as part of the same command. If the minimum and maximum values do not fit into the new data type, an error will be generated.
increment
-
The clause
INCREMENT BY increment
is optional. A positive value will make an ascending sequence, a negative one a descending sequence. If unspecified, the old increment value will be maintained.
minvalue
NO MINVALUE
-
The optional clause
MINVALUE minvalue
determines the minimum value a sequence can generate. If
NO MINVALUE
is specified, the defaults of 1 and the minimum value of the data type for ascending and descending sequences, respectively, will be used. If neither option is specified, the current minimum value will be maintained.
maxvalue
NO MAXVALUE
-
The optional clause
MAXVALUE maxvalue
determines the maximum value for the sequence. If
NO MAXVALUE
is specified, the defaults of the maximum value of the data type and -1 for ascending and descending sequences, respectively, will be used. If neither option is specified, the current maximum value will be maintained.
start
-
The optional clause
START WITH start
changes the recorded start value of the sequence. This has no effect on the
current
sequence value; it simply sets the value that future
ALTER SEQUENCE RESTART
commands will use.
restart
-
The optional clause
RESTART [ WITH restart ]
changes the current value of the sequence. This is similar to calling the
setval
function with
is_called
=
false: the specified value will be returned by the
next
call of
nextval. Writing
RESTART
with no
restart
value is equivalent to supplying the start value that was recorded by
CREATE SEQUENCE
or last set by
ALTER SEQUENCE START WITH.
In contrast to a
setval
call, a
RESTART
operation on a sequence is transactional and blocks concurrent transactions from obtaining numbers from the same sequence. If that's not the desired mode of operation,
setval
should be used.
cache
-
The clause
CACHE cache
enables sequence numbers to be preallocated and stored in memory for faster access. The minimum value is 1 (only one value can be generated at a time, i.e., no cache). If unspecified, the old cache value will be maintained.
CYCLE
-
The optional
CYCLE
key word can be used to enable the sequence to wrap around when the
maxvalue
or
minvalue
has been reached by an ascending or descending sequence respectively. If the limit is reached, the next number generated will be the
minvalue
or
maxvalue, respectively.
NO CYCLE
-
If the optional
NO CYCLE
key word is specified, any calls to
nextval
after the sequence has reached its maximum value will return an error. If neither
CYCLE
or
NO CYCLE
are specified, the old cycle behavior will be maintained.
SET { LOGGED | UNLOGGED }
-
This form changes the sequence from unlogged to logged or vice-versa (see
CREATE SEQUENCE (CREATE_SEQUENCE(7))). It cannot be applied to a temporary sequence.
OWNED BY table_name.column_name
OWNED BY NONE
-
The
OWNED BY
option causes the sequence to be associated with a specific table column, such that if that column (or its whole table) is dropped, the sequence will be automatically dropped as well. If specified, this association replaces any previously specified association for the sequence. The specified table must have the same owner and be in the same schema as the sequence. Specifying
OWNED BY NONE
removes any existing association, making the sequence
"free-standing".
new_owner
-
The user name of the new owner of the sequence.
new_name
-
The new name for the sequence.
new_schema
-
The new schema for the sequence.
NOTES
ALTER SEQUENCE
will not immediately affect
nextval
results in backends, other than the current one, that have preallocated (cached) sequence values. They will use up all cached values prior to noticing the changed sequence generation parameters. The current backend will be affected immediately.
ALTER SEQUENCE
does not affect the
currval
status for the sequence. (Before
PostgreSQL
8.3, it sometimes did.)
ALTER SEQUENCE
blocks concurrent
nextval,
currval,
lastval, and
setval
calls.
For historical reasons,
ALTER TABLE
can be used with sequences too; but the only variants of
ALTER TABLE
that are allowed with sequences are equivalent to the forms shown above.
EXAMPLES
Restart a sequence called
serial, at 105:
-
ALTER SEQUENCE serial RESTART WITH 105;
COMPATIBILITY
ALTER SEQUENCE
conforms to the
SQL
standard, except for the
AS,
START WITH,
OWNED BY,
OWNER TO,
RENAME TO, and
SET SCHEMA
clauses, which are
PostgreSQL
extensions.
SEE ALSO
CREATE SEQUENCE (CREATE_SEQUENCE(7)), DROP SEQUENCE (DROP_SEQUENCE(7))
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- PARAMETERS
-
- NOTES
-
- EXAMPLES
-
- COMPATIBILITY
-
- SEE ALSO
-
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Time: 08:10:30 GMT, April 24, 2024